2002 Jeep Liberty with approximately 130,000 miles.
Engine is misfiring on multiple cylinders. Burnt wire smell and smoke coming from firewall area. After troubleshooting, I believe the engine is running on only one cylinder. Smell coming out of the exhaust is atrocious; does not smell like sulfur but instead unburnt fuel and/or stale gas.
Scanning the vehicle indicates all fuel injectors and all coil packs except for one are malfunctioning due to a circuit issue.
We pulled the coil packs off and looked at the spark. At the end of the spark plug, there was a pale yellow spark. On the working cylinder, it was bright blue. We swapped the two coil packs / plugs and ultimately nothing changed - meaning the originally working coil pack now was providing a pale yellow spark, and vice versa.
Things I have tried: Replacing ECM; no change Cleaning ground wires to ECM and applying conductive grease to the ground; no change
I am stumped and really not sure what the issue could be. Any ideas on what to test next?